The present invention relates to a mobile telephone system, in which more than two different mobile radio telephone systems are used by one mobile radio telephone serving as a single terminal. In particular, the present invention relates to a mobile telephone system which is capable of coping with a plurality of mobile radio telephone systems by the mobile radio telephone downloading software of a predetermined communication protocol etc., for communication by each mobile radio telephone system, using a communication means.
Among a wide variety of conventional mobile systems where various kinds of systems can be selected according to priorities of a user, there is a mobile communication system as disclosed in Japanese Patent Laid-Open Publication No. 08-130766 which is capable of roaming and handing over between different systems.
A TDMA (Time Division Multiple Access) system, a CDMA (Code Division Multiple Access) system, a TDD (Time Division Duplex) system etc. have been used for conventional mobile communication devices. The TDMA system is a kind of system which in case when a plurality of stations in a same band is executing communication at the same time, assigns a particular period of time to the user where the user is able to communicate within that given period of time. The CDMA system is a kind of system which effects multiple access by a spread spectrum communication which spreads an information signal spectrum to a sufficiently wide band as compared to the original information band width. The TDD system is a kind of system in which spread sequence code directly cashes in on the information signals.
Japanese Patent Laid-Open Publication No. 07-222227 discloses a mobile communication device in which such TDMA/TDD system and CDMA/TDD system are combined, where a line of the mobile radio telephone is shared between two systems such that both systems are available for use.
Some examples as to implementation of such different systems to a mobile radio telephone would be, for instance with respect to currently used cellular phone systems in North America, an AMPS using frequency modulation (FM), a TDMA conducting time division multiple accessing using xcfx80/4 DQPSK, a CDMA conducting code division multiple accessing, a N-AMPS in which a band width is narrowed down to about half the AMPS due to frequency modulation etc.
Furthermore, there is a PCS system in which the frequency band of 800 MHz in the above-mentioned system is shifted to 1.9 GHz. It is quite obvious that a variety of systems have been used for the mobile radio telephone.
Regarding the terminals which are used with the above-mentioned systems, compounding of different frequency bands in a dual mode (dual band) has made some progress. For instance, such compounding of different frequency bands is meant for enabling operation in both 1.9 GHz and 800 MHz frequency bands. On the contrary, no attempt has been made to compound completely different multiplex systems (CDMA system and TDMA system).
Under such circumstances, each system has to be specialized, and there have been few occasions where each system would operate mutually.
Therefore, in case when the user wishes to benefit from services offered by various systems, the user has to have a different terminal for each system.
It is therefore an object of the present invention to solve the above-mentioned problems, and to provide a mobile telephone system which is used under a condition that the user does not have to possess an individual mobile radio telephone for each system but a single mobile radio telephone to cope with various systems, which enables the mobile radio telephone to be used in a wider range of service area, and which enables a major decrease in the memory capacity to be installed in the mobile radio telephone. Furthermore, in additionally applying a new communication system, the mobile telephone system of the present invention can cope with downloading of a communication protocol, and even when there are minor changes in the software of the mobile radio telephone, the mobile telephone system is capable of updating the software.
In order to achieve the above object, the present invention provides a mobile radio system comprising: a first base station corresponding to a first mobile radio telephone system; a second base station corresponding to a second mobile radio telephone system; and a mobile radio telephone, within a communication area of either said first base station or second base station, following a predetermined initial data communication protocol to compare a first mobile radio telephone system flag transmitted from said first base station or a second mobile radio telephone system flag transmitted from said second base station with an existing mobile radio telephone system flag to see whether they coincide with each other or not, and in such case when the two system flags coincide with each other, executing a mobile radio telephone communication in accordance with an existing mobile radio telephone communication protocol, while in such case when the two system flags do not coincide with each other, following said initial data communication protocol of the communication area of either said first base station or second base station where said mobile radio telephone is located at, so as to download a first or a second mobile radio telephone communication protocol software, and to execute a mobile radio telephone communication within said first or second communication area after downloading is completed.
In accordance with the present invention, in case when the mobile radio telephone is located inside the communication area of the first base station, the first mobile radio telephone system flag transmitted from the first base station and the existing second mobile radio telephone system flag transmitted from the second base station are compared, following the initial data communication protocol. When the first mobile radio telephone system flag and the existing second mobile radio telephone system flag coincide with each other, the existing mobile radio telephone communication protocol software being used in the previous communication is used to execute a mobile radio telephone communication.
On the other hand, when the first mobile radio telephone system flag and the second mobile radio telephone system flag do not coincide with each other, the first mobile radio telephone communication protocol software used in the first base station is downloaded, after which a mobile radio telephone communication starts in the communication area of the first base station.
Furthermore, in case when the mobile radio telephone moves from the communication area of the first base station to the communication area of the second base station, the second mobile radio telephone system flag transmitted from the second base station and the existing first mobile radio telephone system flag transmitted from the first base station used in the previous communication are compared in accordance with the initial data communication protocol, and since they are different, the second mobile radio telephone communication protocol software used in the second base station is downloaded on the basis of the initial data communication protocol, after which a mobile radio telephone communication starts in the communication area of the second base station.
Therefore, in accordance with the present invention, a single mobile radio telephone can cope with various systems, which enables the mobile radio telephone to be used in a wider range of service area, and which enables a major decrease in the memory capacity to be installed in the mobile radio telephone. Moreover, in additionally applying a new communication system, the present invention can cope with downloading of a communication protocol, and even when there are minor changes in the software, the system is capable of updating the software.